The present invention relates to an antimicrobial conveyor lubricant composition and to a method for using an antimicrobial conveyor lubricant composition.
In the commercial distribution of most beverages, the beverages are packaged in containers of varying sizes, such containers being in the form of cartons, cans, bottles, tetrapack packages, waxed carton packs, and other forms of containers. In most packaging operations, the containers are moved along conveying systems, usually in an upright position (with the opening of the container facing vertically up or down), and moved from station to station, where various operations are performed (e.g., filling, capping, labeling, sealing, etc.). The containers, in addition to their many possible formats and constructions, may comprise many different types of materials, such as metals, glasses, ceramics, papers, treated papers, waxed papers, composites, layered structures, and polymeric materials (e.g., especially polyolefins such as polyethylene, polypropylene, polystyrene, blends and laminates thereof, polyesters such as polyethyleneterephthalate and polyethylenenaphthalate, blends, and laminates thereof, polyamides, polycarbonates, etc.).
There are a number of different requirements that are essential or desirable for antimicrobial lubricants in the conveying systems used to carry containers for beverages. The essential requirements are that the materials provide an acceptable level of lubricity for the system and that the lubricant displays an acceptable antimicrobial activity. It is also desirable that the lubricant has a viscosity which allows it to be applied by conventional pumping and/or application apparatus (e.g., spraying, roller coating, wet bed coating, etc.) as commonly used in the beverage conveyor lubricating art, and that the lubricant is beverage compatible so that it does not form solid deposits when it accidentally contacts spilled beverage on the conveyor system. This last requirement can be especially important since the formation of deposits on the conveyor will change the lubricity of the system and could require shut-down of the equipment to facilitate cleaning. Deposits may occur from the combination of beverage and lubricant in a number of different chemical methods, depending upon the particular beverage and lubricant used. One of the more common forms of deposit is caused by the formation of micelles or coacervates from the interaction of species, especially different ionic species within the two materials.
Different types of lubricants have been used in the beverage conveying industry with varying degrees of success. A more common type of lubricant is the fatty acid lubricant (either the acid itself or amine salt and/or alkali metal salts and/or ester derivatives thereof), some of which are described in U.S. Pat. No. 5,391,308. Another type of lubricant used within this field is the organic phosphate ester, as shown in U.S. Pat. No. 4,521,321 and PCT Application WO 96/02616, based upon British Patent Application 94/14442.5 filed Jul. 18, 1994 (PCT/GB95/01641).
U.S. Pat. No. 5,391,308 discloses phosphate esters other than alkyl or linear esters (e.g., the alkyl aryl phosphate esters described on column 6, lines 11-20 used in combination with the alkyl or linear phosphate esters). The lubricant system of this patent also requires the use of an aqueous based long chain fatty acid composition at a pH of from 9.0 to 10.5 as the lubricant, with specifically combined ingredients to avoid stress cracking in polyethylene terephthalate (PET) bottles transported on a conveyor system. The aromatic-polyoxyalkyl esters are specifically disclosed as part of a combination of esters (along with the alkyl esters) which
xe2x80x9c. . . results in substantial reduction in stress cracking, thus fuinctioning as the stress cracking inhibiting agent, as well as the emulsifying agent, in the aqueous lubricant concentrate.xe2x80x9d
See U.S. Patent No. 5,391,308 at column 3, lines 48-52. The reference is specific to fatty acid lubricants, and the specification points out that the use of potassium hydroxide as the saponifying agent, in fatty acid lubricants, has been found to contribute to and to promote stress cracking in PET (polyethylene terephthalate) bottles. A blend of alkyl phosphate esters and aromatic phosphate esters are shown in combination with the fatty acid lubricant to reduce stress cracking.
PCT Application WO 96/02616 describes the use of lubricant concentrates comprising organic alkyl phosphate esters, aromatic biocidal quaternary ammonium compounds, and sufficient base to provide the concentrate with a pH of from 5 to 10.
U.S. Pat. No. 4,521,321 describes lubricants for conveyor systems that comprise dilute aqueous systems of partially neutralized monophosphate aliphatic (e.g., saturated or partially unsaturated linear alkyl). The use of a synergist such as long chain fatty alcohol, fatty acid derived amine oxide, or urea improves the properties of the lubricant.
U.S. Pat. No. 5,062,979 describes lubricants for conveyor systems comprising aqueous, clear solution-forming, substantially soap-free compositions. These lubricants comprise pH 6-8 compositions comprising alkyl benzene sulfonates, partial phosphate esters with alkoxylated aliphatic alcohols, and aliphatic carboxylic acids. Typical additives such as solubilizers, solvents, foam inhibitors and disinfectants may also be present. The aliphatic carboxylic acids are C6-C 12 fatty acids.
U.S. patent application U.S. Ser. No. 09/002,796, titled xe2x80x9cANTIMICROBIAL, BEVERAGE COMPATIBLExe2x80x9d and filed on Jan. 5, 1998 describes lubricating compositions, especially designed for use in beverage conveying systems for contained beverages. The lubricating compositions can include:
a) an alkyl alkoxylated (e.g., ethoxylated or propoxylated, preferably ethoxylated) phosphate ester,
b) aryl (e.g., aromatic, such as phenol) alkoxylated (e.g., ethoxylated or propoxylated) phosphate ester,
c) an aromatic or linear quaternary ammonium antimicrobial agent, and
d) a liquid carrier, such as water.
Particularly desirable optional agents include chelating agents (e.g., the aminoacetic acid chelating agents such as ethylene diamine tetraacetic acid, EDTA), detergents (e.g., nonionic surfactants) and pH control agents (e.g, potassium or sodium hydroxide).
An antimicrobial conveyor lubricant composition is provided according to the invention. The antimicrobial conveyor lubricant composition includes an alkyl alkoxylated phosphate ester, an antimicrobial agent, water, and neutralizing agent in an amount sufficient to provide an antimicrobial lubricant composition use solution with a pH in the range of about 4 to about 9. The lubricant composition can preferably be characterized as a non-fatty acid lubricant based antimicrobial conveyor lubricant composition. The lubricant composition can additionally include extreme pressure additive, corrosion inhibitor, and viscosity control agent. Preferred viscosity control agents include secondary alcohol alkoxylates, aromatic alkoxylated phosphate esters, and mixtures thereof.
A method for using an antimicrobial conveyor lubricant composition is provided according to the invention. The method includes a step of applying the antimicrobial conveyor lubricant composition use solution to a conveyor. In general, the antimicrobial conveyor lubricant composition use solution is prepared by diluting an antimicrobial conveyor lubricant composition concentrate with water to provide a use solution having an active level of between about 0.1% and 1%.